Torque reduction tool

ABSTRACT

A tool for reducing torque on work string, eg for gas or oil production, comprises an upper clamp ( 2 ), a lower clamp ( 3 ) and connection means ( 4 ), the three components formed as a unitary structure ( 1 ). The tool also comprises bearing means, preferably made from an elastomeric compound, and an annular body ( 7 ) (see FIG.  4 ) held in place over the connection means by the clamps. The clamps may comprise spigots ( 5 ) for retaining the connection means. In a preferred embodiment the annular body is in two semi-annular components connected at one end to allow them to pivot, and the other end comprises mating castellations for receiving a fastening pin. The annular body may comprise a number of replaceable wear pads ( 14 ) which may be made of bronze or an elastomer. The unitary structure of the tool enhances the integral strength and efficiency of the clamps.

The present invention relates to a torque reduction tool, as istypically used with a work string in gas and oil production.

Well bores are conventionally created using a drill bit attached to astring of drill pipe, commonly known as a “work string” or “drillstring”, which is advanced into the new bore from the surface. The newlydrilled section of the well bore is then lined with structural casingwhich is cemented in place when set.

As a work string is passed through a bore, which has already been lined,it frequently contacts the casing, and as a result, the rotationalmovement of the work string gradually wears the casing wall. Such wearis enhanced by abrasive mud particles typically found within a downholeenvironment. Furthermore, frequent contact between the casing and toolstring causes torque and drag which hinder rotation of the work stringand impedes progress of the string along the bore.

Torque and wear are especially problematic during drilling processeswhich require the work string to be progressed along a curved path. Inhorizontal or extended wells, both friction and torque are increased asa result of the increased contact between the work string and casing.

It is known in the art that fitting a protector to the tool string mayreduce both rotary torque and casing wear. Conventionally, suchprotectors are comprised of an annular body which fits around the workstring. U.S. Pat. No. 50,069,297 teaches of a work string protectorwhich is comprised of a protective sleeve mounted on a length of drillpipe which prevents damaging contact between the tool string and casingwall. The protector is secured to the tool string via independent clampsor “thrust bearings” which are removably attached to the tool stringabove and below the protective sleeve thereby leaving a separate narrowworking clearance at either end.

While this protector mitigates casing wear and reduces torque, theefficiency of the clamps which are independent of the torque reductiontool and which hold the protector in place are tested in the downholeenvironment where hostile chemical conditions, high loading, andtemperature are prevalent. In particular, in the event that the veryhigh loading and rotational movement of the work string tears the clampsfrom the work string the clamps are left free to obstruct the passage ofany further apparatus in the bore. Furthermore, if a clamp is broken offin such a manner, or if it slips independently along the work string,the protector can move longitudinally along the work string, in thedirection which was previously restricted. In this circumstance theprotector can easily become detached from the work string. Therefore aseach of the components in conventional torque reduction tools areindividual entities, protecting ability is lost even if only one of theclamps fails and the other remains intact. It would therefore beadvantageous to provide a torque reduction tool wherein the strength ofthe clamps is enhanced by the structural integrity of the torquereduction tool and clamps, so that in the event of one of the clampsfailing the remaining clamp would still be able to retain the torquereduction tool in place on the work string.

It is an object of the present invention to provide a torque reductiontool which reduces casing wear and torque produced by the rotation of awork string in a well bore.

It is a further object of the present invention to provide a torquereduction tool with superior clamping qualities which fixes the positionof the protector in a stationary position on the work string.

It is a further object of the present invention to provide a torquereduction tool wherein the clamps which hold the torque reduction toolin place form a unitary mechanical structure with the other componentsof the tool.

According to a first aspect of the present invention there is provided atorque reduction tool comprising upper and lower clamps and a connectionmeans, wherein the upper and lower clamps and connection means combineto form a unitary mechanical structure, and wherein the torque reductiontool further comprises bearing means for providing a low frictioncontact between the tool and pipe or casing, the bearing means beingprovided on an annular body which is held in place, over the connectionmeans, by the upper and lower clamps.

Preferably the upper and lower clamps are constructed from bronzealthough any other material suitable for bearing tensile or compressionloads could be used.

Preferably the connection means is constructed from steel although anyother material suitable for bearing tensile or compression loads couldbe used.

Preferably each clamp is comprised of two or more part annularcomponents which are connected by hinges.

Alternatively each part annular component has a formation at onerespective end, wherein the formations of the part annular componentscan co-operate with each other to allow them to pivot.

Preferably each clamp has retaining means, spigot or the like, forreceiving said connection means.

Preferably the annular body has replaceable wear pads on the externalsurface of the body.

Preferably the replaceable wear pads of the annular body are made from arelatively resistant and hard wearing material such as bronze, althoughany other suitable material could be used.

Alternatively the wear pads are made from a soft, sacrificial materialsuch as an elastomer.

Preferably the sacrificial wear pads are replaceable.

Preferably the bearing means is made from an elastomeric material.

Preferably the bearing means is fixed to the annular body in such amanner that the bearing means does not move relative to the annularbody.

Preferably the bearing means is fixed to the annular body by screwswhich fit into corresponding elements in the bearing means and annularbody.

Typically the annular body is made of a soft metallic material such asaluminium although any other suitable material could be used.

Preferably the annular body is comprised of two semi annular components.

Preferably the semi annular components are connected at onecircumferential end by hinges.

Preferably the semi annular components have a second circumferential endwith mating means.

Preferably the clamp has receiving means for accepting a pin or thelike.

Also according to the present invention there is provided a torquereduction tool, comprising an upper and lower clamp and annular body,wherein at least one of the upper and lower clamps has receiving meansfor receiving a pin or the like, wherein the pin can pass through thereceiving means of the clamp into corresponding receiving means in theannular body and wherein the clamps are adapted to block subsequentpassage of the pin.

According to a second aspect of the present invention there is provideda method for securing a torque reduction tool around a work string, thetorque reduction tool comprising an upper and lower clamp and connectionmeans and an annular body which is positioned on the work string betweensaid clamps, using a pin which fits into receiving means in the upperclamp and corresponding receiving means in castellations on the annularbody, comprising the steps of:

-   -   A) positioning the integral clamp and connection means on the        work string via bolting or the like;    -   B) positioning the annular body around the workstring in between        said clamps;    -   C) passing a pin or the like through the receiving means of the        upper clamp and into the receiving means of the annular body        castellations thereafter.

An example embodiment of the invention will now be illustrated withreference to the following Figures in which:

FIG. 1 is a half section diagram showing the assembly of a torquereduction tool on a work string in accordance with the presentinvention;

FIG. 2 is an elevated view of an annular body component in isolation;

FIG. 3 is a side view of an annular body component in isolation, and;

FIG. 4 is a torque reduction tool as assembled on a work string.

Referring firstly to FIG. 1 a torque reduction tool, generally depictedat 1, is comprised of an upper 2 and lower clamp 3, and connection means4. Both the upper 2 and lower 3 clamps have spigots 5, into which theconnection means 4 fits, wherein on connection of the connection means 4to the upper 2 and lower 3 clamps a unitary mechanical structure isformed.

To assemble the torque reduction tool, the connection means 4 is used tojoin clamps 2 and 3. The clamps 2 and 3 are essentially identical butare referred to from here on as an upper and lower clamp to describe theultimate position of each on the work string. The connection means 4 fitinto spigot structures 5 on the clamps which act to retain theconnection means 4 in place, and in this manner a unitary mechanicalstructure is constructed. However the advantage of the structure shownis that, whilst it is a single structural unit, it incorporates threeseparate components which can be replaced individually if required. Thestructure is fastened onto the section of work string (not shown) whereprotection and torque reduction is required and secured usingappropriate fixing means such as bolts or screws 6.

FIGS. 2 and 3 show alternative views of the annular body, which isgenerally depicted at 7. The annular body 7 is comprised of two semiannular components 8 and 9 which are hinged together at 10 to allow theannular body to be opened in order to fit over the work string (notshown). The annular body 7 further comprises castellations 11 which comeinto alignment when the annular body 7 is closed around the work string.The castellations 11 have receiving means 12 which run centrally throughthe length of the castellations 11 and are shaped to receive a fastener,typically a pin 13, which holds the two semi annular components 8 and 9closed around the work string. The annular body 7 also has wear pads 14on the external surface, which are constructed from a hard wearingmaterial such as bronze and can be replaced if required. In the presentembodiment the replaceable wear pads 14 are arranged on the annular body7 as strips which run the entire longitudinal length of the body,although any other suitable design could be used. The wear pads 14 arethe first point of contact between the casing and the annular body 7 andtherefore act sacrificially to increase the lifespan of the annular body7 itself.

FIG. 4 shows the torque reduction tool as it appears when assembled on awork string (not shown). The upper 2 and lower 3 clamps are heldtogether by the connection means (not shown). The protective annularbody 7 sits over the connection means on the work string and between theupper 2 and lower 3 clamps. The torque reduction tool further comprisesbearing means (not shown) which are constructed from an elastomericmaterial and are attached to the internal surface of the annular body 7.The work string encased by the torque reduction tool is free to rotaterelative to the annular body 7 and bearing means and is therefore notobstructed from performing its normal function.

The annular body 7 can be fitted over the work string as it is comprisedof two semi annular components 8 and 9 which are hinged together. Thesemi annular components are closed around the work string, aligning themating castellations 11 of the semi annular components 8 and 9. Themating castellations 11 and upper clamp 2 have receiving means 15 a and15 b for receiving a fastening pin, 13. To secure the annular body 7shut, the receiving means 15 a of the upper clamp 2 and receiving means15 b of the annular body castellations 11 are aligned. The fastening pin13 can then be passed through the receiving means 15 a of the upperclamp, into the receiving means 15 b of the annular body castellations.

The advantage of the present invention is that the clamps and torquereduction tool are integrated into a unitary mechanical structure. Theintegral strength and efficiency of each of the clamps is thereforeenhanced as each clamp is supported by the rest of the tool and cantherefore effectively restrain the torque reduction tool in place, atloading levels and under circumstances where a non-unitary design wouldhave failed. This ensures that the torque reduction tool is retained onthe section of the work string that it is required.

Further modifications and improvements may be incorporated withoutdeparting from the scope of the invention herein intended.

1. A torque reduction tool, comprising an upper and lower clamp and aconnection member, wherein the upper and lower clamps and connectionmember combine to form a unitary mechanical structure, and wherein thetorque reduction tool further comprises one or more bearing members forproviding a low friction contact between the tool and pipe or casing,the bearing members being provided on an annular body adapted to fitabout an outer diameter of the connection member, and held in place bythe upper and lower clamps, wherein at least one of the upper and lowerclamps has a receiving portion for receiving a pin or the like, whereinthe pin can pass through the receiving portion of the clamp into acorresponding receiving portion in the annular body and wherein thedamps are adapted to prevent the pin from exiting from either receivingportion.
 2. A method for securing a torque reduction tool around a workstring, the torque reduction tool comprising an upper and lower clampand a connection member and an annular body which is positioned on thework string between the damps, using a pin which fits into a receivingportion in the upper clamp and corresponding receiving portion incastellations on the annular body, comprising: A) positioning theintegral clamp and connection member on the work string; B) positioningthe annular body around the work string in between the clamps; and C)passing a pin or the like through the receiving portion of the upperclamp and into the receiving portion of the annular body castellations.3. The method of claim 2, wherein the work string is rotatable relativeto the annular body.
 4. The method of claim 2, further comprisingpositioning one or more bearings mechanisms between the annular body andthe connection means to allow rotation of the annular body relative tothe work string.
 5. A torque reduction tool comprising upper and lowerdamps and a connection member, wherein the upper and lower damps andconnection member combine to form a unitary mechanical structure, andwherein the torque reduction toot further comprises one or more bearingmembers for providing a low friction contact between the tool and pipeor casing, the bearing members being provided on an annular body whichis held in place, over the connection member, by the upper and lowerclamps, wherein the upper and lower clamps are constructed from bronze.6. A torque reduction tool comprising upper and lower clamps and aconnection member, wherein the upper and lower damps and connectionmember combine to form a unitary mechanical structure, and wherein thetorque reduction tool further comprises one or more bearing members forproviding a low friction contact between the tool and pipe or casing,the bearing members being provided on an annular body which is held inplace, over the connection member, by the upper and lower clamps,wherein each clamp has a retaining portion for receiving the connectionmember.
 7. The torque reduction tool of claim 6, wherein the retainingportion is a spigot.
 8. A torque reduction tool comprising upper andlower damps and a connection member, wherein the upper and lower dampsand connection member combine to form a unitary mechanical structure,and wherein the torque reduction tool further comprises one or morebearing members for providing a low friction contact between the tooland pipe or casing, the bearing members being provided on an annularbody which is held in place, over the connection member, by the upperand lower clamps, wherein the bearing member is fixed to the annularbody by screws which fit into corresponding elements in the bearingmember and annular body.